Glycolytic function in goldfish hepatocytes at different temperatures: relevance for Na+ pump activity and protein synthesis

G Krumschnabel, S Malle, P J Schwarzbaum, W Wieser
1994 Journal of Experimental Biology  
Cellular metabolism of ectotherms may respond to temperature changes with a shift in the choice of substrate preferentially catabolized for ATP production (Johnston and Dunn, 1987) . This has been shown in acclimated fish, in which a temperature-dependent switch from carbohydrates as the main fuel for energy metabolism to other fuels, or vice versa, can occur. Such shifts help to indicate the relative importance of aerobic glycolysis as an ATP-supplying process. The preferred energy source at a
more » ... energy source at a given temperature depends upon the temperature range investigated, as well as on the species, on the tissue and upon nutritional factors. The adaptive significance of shifts between energy sources is not always clear. While in some cases ecological arguments may provide plausible explanations (e.g. seasonal adaptation to migration and reproductive requirements; Stone and Sidell, 1981; Moerland and Sidell, 1981) , evidence is accumulating that structural or functional features inherent in the metabolic organisation of the cell may also play a role in determining the nature of such responses (Sidell, 1983; Sidell and Hazel, 1987) . Of particular relevance in this respect is the interaction between diffusional flux and the rate of enzymatic activity in shaping specific temperature effects on cellular metabolism. We studied this problem by subjecting isolated goldfish hepatocytes to acute temperature changes and measuring the rate of total and function-related metabolism both in the presence and in the absence of the glycolytic inhibitor iodoacetic acid (IAA). Using this approach, we hoped to learn to what extent the temperature relationships of different metabolic functions depended upon the site of ATP production and thus on the distribution of these sites within the cell. Goldfish (Carassius auratus L.) were obtained from commercial suppliers and were kept in 100 l aquaria at 15˚C. The fish were killed and hepatocytes were isolated from freshly excised livers as described in detail elsewhere (Krumschnabel et al. 1994 ). The final cell pellet was resuspended in Hepes-buffered saline (in mmol l Ϫ1 : 135 NaCl, 3.8
pmid:7931037 fatcat:fv7xudertbb2vkcerhy6dwevmi